Identity of NEWLY DISCOVERED SYNC FLASHER

Philip Chien (kc4yer@amsat.org)
Thu, 31 Jul 1997 02:03:31 -0400

Ron Lee said:

>>Thanks Philip,  I assumed you would answer this question.  Since
>>it is 3-axis stabilized, why would it exhibit characteristics
>>associated with spinning/tumbling?

Anthony Beresford <starman@camtech.net.au> said:

>Perhaps they use momentum wheels for stabilization, mainly
>and have [presumably on a scheduled maintenance basis] taken
>the satellite out of service while they slowly spin( using gas jets) it to
>dump the angular momentum of the wheels/gyros?

nope.  If a three-axis stabilized television satellite was to spin for any
reason it wouldn't be able to keep its antenna locked on the Earth.  And
that would tend to annoy the customers (like NBC ...)

When the momentum wheels are desaturated they're just spun down.  A
saturated wheel is one which is running at full speed and desaturation ist
slowing it down.  The laws of conservation of angular momentum will cause
the spacecraft to spin the opposite directn of the wheel, so the attitude
maintenance jets are used to counteract that force.  During the entire
desaturation process the spacecraft remains stable.


I don't think Jay saw GE-1 (1996-54A).  But I do think he saw something
even more fascinating - Telstar 401 (1993-77A).  It's currently at 102.2
degrees, and drifting .4 degrees West each day.  It looks like we've got
another Superbird situation with the entire world having the opportunity to
see a derelict out-of-control satellite as it drifts West each day!


Now Jay, couldn't you have spotted this several months ago when I could
have used that information in my article on the death of Telstar 401????

*sigh*

I believe there's a JPG of the satellite at the Skynet web page.  Look for
Telstar 402R (its sister satellite).  For obvious reasons I doubt that
Skynet wants to talk much about Telstar 401.  The web page's address was
http://www.att.com/skynet/ before the Skynet divisin was sold to Space
Systems Loral.  It's possible the web address may have changed due to the
sale.


Telstar 401 was the first GE-7000 satellite.  It was launched in December
1993, about a week after the first Hubble servicing mission.  (you remember
- the mission where the aforementioned Jay spotted the discarded solar
array one orbit *before* me!).  The satellite failed in January 1997.

While it's roughly the same size as the Superbird they are made by
different manufacturers.  (Superbird is a Space Systems Loral FS-1300).

If you want to help keep me in business, check out the March/April 1997
issue of "Satellite Times" for my story on the Telstar 401 failure.



Philip Chien [M1959.05.31/31.145//KC4YER@amsat.org]